A good week for defense

I successfully defended my dissertation last Thursday! Defense title: “Measured and modeled albedos of sea-ice surfaces on the oceans of Snowball Earth.”

Here’s how I summed up my talk:

A planet orbits round a yellow sun
Light years away or megayears ago
Its seas are dark, its continent is dun
But brilliant sea ice sets its pole aglow

Its CO2 drops dangerously low
Tendrils of ice reach from the polar caps
That sparks a feedback: oceans turn to snow,
Glaciers push in to close off any gaps

The oceans roiled with countless living cells
Who learned to take their energy from light
Now locked beneath the cold of Dante’s hells
They starve; how long must they endure this night?

Why has this happened, and by what device?
To know, we must investigate the ice.

As sea ice freezes, tiny drops of brine
Are trapped between the quickly forming plates
When cold enough, their molecules align
Into sodium chloride dihydrates

The solid crystals catch and scatter light
Reflect it back, refuse its energy
And I myself have quantified how bright
The surface of the sub-eutectic sea

And in our lab we’ve watched salt ice sublime
With instruments ingeniously designed
The secrets of another space and time
Unfold beneath my models and my mind

This is my work; I hope you will agree
That it is worthy of a Ph.D.

Ice Needles (not to be confused with Space Needles)

Yesterday on my way to the office I noticed that the ground looked weird. Inspecting it more closely I discovered that the apparent “surface” was actually composed of lots of dirt clods and small rocks on top of two-inch-tall pillars of ice.

All of these rocks and bits of dirt are on 2-inch-tall ice columns

I had never seen anything quite like it before, at least not in person. The physics involved is actually quite complicated and I don’t fully understand it myself, but it boils down to something like this: if ice is freezing at some particular spot, it “pulls” water toward itself. You mostly see this effect in porous materials that water can flow through by capillary action, like soil.

So the water gets pulled toward the ice and freezes on to it, pulling yet more water along behind it, and gradually more and more ice forms. In this case you end up with columns that lift pebbles off the ground, a.k.a. needle ice. In other cases, where the freezing is happening underground, you can get frost heaves or weird permafrost landforms (this is called ice segregation.

You can see the ground through the hole.

An ice column I plucked out to examine.

Under the bushes the columns got surreally twisted.

Side view of the ice columns lifting some pebbles and a small ice sheet

You can see there was a change in the freezing process; the short, whiter columns seem to have been lifted by the taller, darker columns underneath. The bottoms of the small columns have frost on them.

Side view.

More images here.

Notes from a Defense (cross-posted from S.A.G.A.N.)

I wrote this while my friend and colleague Marcela Ewert presented her work at her Ph.D. defense. She’s been doing a lot of really cool work about how Arctic microbes make their living despite the temperature and salinity extremes found in the sea ice and in the snow that rests on it. Here’s a link to some of the work included in her dissertation.

Jargon note: exopolysaccharides, also known as extracellular polysaccharides or EPS, are substances secreted by microbes (bacteria, algae, etc.) You may be familiar with extracellular polysaccharides like xanthan gum, which is produced by a soil bacterium and used as a thickener by the food industry. The exopolysaccharide produced by the Arctic microbes Marcela studies seems to be especially good at sticking to ice.

Colwellia and Psychrobacter are both species of sea-ice-dwelling bacteria.

Bacteria in Arctic Sea Ice and Salty Snow

Our universe is full of water ice
Whose particles in stellar-forming clouds
Are substrates on which molecules can splice
To veil the ice in thin organic shrouds.
On Earth, the ice on mountains and near poles
Plus snow and sea ice makes the cryosphere
In cold ecologies it plays its roles;
Sea ice and salty snow concern us here.

As sea ice forms, its icy fingers reach
Encapsulating nets of salty brine
And with the salty water, many creat-
ures will be trapped–by chance, or by design?
Bacteria and algae both secrete
Ice-loving exopolysaccharide
Which grips the icy matrix to defeat
The brine flow that would carry them outside
But in snow, changing temperatures and salt
To microbes like Colwellia spell doom
While Psychrobacter lives through this assault
And finds home where Colwellia finds a tomb.

But with the proper solutes all can thrive
And Arctic ice and snow can come alive.

Scatter, Adapt and Remember (cross-posted from S.A.G.A.N.)

Note: S.A.G.A.N. is a social network for astrobiologists, and I have promised I will write some poems for them. Like this one!

Last month I went to see a talk by Annalee Newitz of io9.com about her new book, Scatter, Adapt and Remember. In the talk, she went over some of Earth’s previous mass extinctions and their notable survivors, and discussed how humanity might manage to make it through the next one, whatever its cause might be.

It was an excellent talk and it inspired me to write the following poem.

Scatter, Adapt and Remember
inspired by Annalee Newitz

Four billion years after the Earth coalesced,
in the Cambrian period, life held a fest-
ival of evolution that still holds us rapt.
Lesson the first: to adapt.

Life took this to heart with impressive effect,
but the number of species has not grown unchecked.
Several times mass extinctions remorselessly zapped
All species that couldn’t adapt.

The survivors escaped from conditions grown harsh
by leaving their homeland of forest or marsh
for new habitats change hadn’t managed to shatter.
Lesson the second: to scatter.

They carried on re-population apace,
and their many descendants took over the place–
till disaster re-taught them the two things that matter:
how to adapt and to scatter.

They evolved new skills after each terrible blight,
like lungs, and warm-bloodedness, uteri, flight.
Then one kindled bright flames from a neuronal ember
and learned Lesson Three: to remember.

For a species had suddenly mastered the means
to store useful skillsets outside of its genes.
All able to learn from their cleverest member
how to scatter, adapt and remember.

When the next big volcano or meteor hits
We’ll survive through our cities, our brains and our bits
We’ll weather the storms of a years-long December⁽¹⁾
And scatter, adapt and remember.

(1) e.g. snowstorms if your reference point is in Canada, firestorms if in Australia, torrential rains in Brazil, etc. There are a wide variety of disastrous Decembers to choose from.

Interstellar Ice

A couple of days ago I gave a talk at the Astrobiology Seminar about organic chemistry—IN SPAAAAACE. I chose the topic because I didn’t actually know anything about it to start out, so I learned a lot of cool stuff researching the talk. One of the things I learned is that ice (note that at ten degrees above absolute zero, “ice” can include things like frozen methane and ammonia as well as our old favorite water ice) is actually quite important to the formation of molecules in interstellar dust clouds.

The Trifid Nebula, a hotbed (coldbed?) of interesting chemistry. From http://apod.nasa.gov/apod/ap130128.html.

Ice accumulates on tiny bits of rocky or sooty dust at the blazing rate of one molecule per day, and then acts as a surface on which chemical reactions can take place. Atoms and molecules just zipping around on their own tend to bounce off of each other, but on the surface of an icy grain they have time to get acquainted and engage in a little friendly covalent bonding. A surprising number of molecules can be built this way, including familiar ones like acetic acid, acetone, and ethanol.

Interstellar ice-grain chemistry could even be partly responsible for the “handedness” of chemistry on Earth, since circularly polarized starlight is one of the few known ways to create a bias toward left- or right-handed chemistry. What I didn’t know until researching this talk is that amino acids with a preference for left-handedness over right have actually been found in asteroids. The going theory is that a small initial bias toward left-handedness, perhaps created by interstellar polarized light, could have been amplified by as-yet-unknown chemistry inside the asteroid. Mystery!

The Very Model of a Modern Glaciologist

A “poster preview video” for the 2012 IGS meeting in Fairbanks. This is about the same project I’ll be presenting at AGU.

Lyrics:
I am the very model of a modern glaciologist
I’m master of all manner of arcane and icy knowledges
My derivation of the flow law rivals that of Dr. Glen
My icy glare can cause a melting glacier to refreeze again
My glacier surveys show my unmatched skill with a theodolite
I outdrink all my colleagues after seminar on Thursday night
The NSIDC sends me their data sets to analyze
I leap crevasses meters wide to save an ice core from demise

I’m here to demonstrate to you this model stuffed with elegance
Developed with the use of my superlative intelligence
It seeks to show why graphs of crystal fabric from depths Stygian
Can oscillate and swivel in a manner callipygian
The foremost of our multitude of possible hypotheses
Was that the ice preserved the stamp of ancient surface processes
To substitute for nonexistent measurements empirical
We based it on pure physics from the realm where cows are spherical

I reasoned that since snowflakes sometimes grow as columns, some as plates
Why shouldn’t grains within the snowpack lend themselves to sim’lar fates?
I made ten thousand crystals and then grew them all stochastically
And let simple diffusion change their size and numbers drastically
The output is a credit to my wit and perspicacity
And several high-speed processors all running at capacity
Come marvel at my poster and admire all my knowledges
For I’m the very model of a modern glaciologist

McCarthy Glaciology Summer School 2010: In Limerick Form

These are some limericks I wrote while attending the 2010 Glaciology Summer School in McCarthy, Alaska. I tried to write one about each subject that was covered in lecture, although I think there are a few missing. N.B.: the tidewater-glacier-as-leveraged-bank analogy is from the actual lecture.

Ice dynamics
Though its speed is exceedingly low,
Ice is fluid, as glacier shapes show.
Non-Newtonian viscosity
Determines velocity
According to Glen’s law of flow.

Ice fabric and anisotropy
At the microscale, ice grain migrations
Derive from crystalline dislocations
Anisotropies cause
New constitutive laws
To account for in our simulations.

Subglacial hydrology
Water flows through the glacier like blood
Makes it slide over bedrock and mud
When a tunnel melts through
Or ice dam breaks in two
Out comes pouring a Biblical flood

Tidewater glaciers
When these tidewater glaciers retreat
The destruction’s both fast and complete
It advances again
On a borrowed moraine
Like a leveraged bank on Wall Street

Mass balance
Adding up rain, wind, heat, cloud and sun
To get melt isn’t very much fun
You could try degree-day
It’s an easier way
But a somewhat less accurate one

Glacial thermodynamics
Now the species of glaciers are three
Cold are fully below zero C
Temperate’s always at freezing
Polythermal’s a pleasing
Combination of types A and B

Remote sensing with ICESat
When inspecting the tracks of ICESat
Look for spots that are curiously flat
Or locations that flex
From concave to convex
It’s a subglacial lake doing that!

Gravitational remote sensing
For the weighing of glaciers, a scale
Is inevitably much too frail
But science saves face
By celestial GRACE
Which delivers the mass-balance Grail

Laser Altimetry
To determine an ice-surface height
Send out regular pulses of light
Measure time to bounce back
Then, repeating your track
Demonstrates warming glaciers’ dire plight

Inverse methods
To extrapolate former conditions
Using presently measured positions
Although methods inverse
May inspire you to curse
They’ll reveal past climatic transitions

Debris-covered glaciers
Grand white Kennicott looms above town
But its foot is all filthy and brown
If we clean off the sand
It’ll look mighty grand
Till, uncovered, it melts, and we drown.

The consequences of setting forty glaciologists loose on a small town’s alcohol supply
There’s a flow law for ice strain and shear
What we need is a flow law for beer
Given glacier grads, N,
And a drink rate X, when
Will all booze on the shelves disappear?

The Story of Glacier Joe

Written at the request of the President of the International Glaciological Society, for the 2012 IGS meeting in Fairbanks. In the style of the classic The Cremation of Sam McGee by the great Robert W. Service.

The Story of Glacier Joe

There are strange things done ‘neath the midnight sun
   By the folks who study ice
They’ll spend hours of time on a glacier climb
   Just to check on some strange device.
With their crampons donned they ascend beyond
   The realms where sane folk go
Yes, they’re all bizarre, but the oddest by far
   Was the one called Glacier Joe.

The letters I.D. marked his sole degree–
   “That’s ‘Doctor of Ice’,” he’d say
From a glacial perch he’d perform research
   In his own peculiar way.

He’d carefully take his ablation stake
   Back home at the start of spring
For the sunny glare might cause wear and tear
   If snowmelt exposed the thing.
He hated to dig, so his snowpit rig
   Was a big overclocked hair dryer
He never would change, though his numbers were strange
   And his notebook often caught fire.

I answered an ad for a glacier grad
   That’s how I joined Joe’s lab
He’d heard some stories ’bout inventories
   And wanted to take a stab.
Our first sortie was altimetry
   With a stopwatch and big flashlight
But so blindingly fast those light pulses went past
   That our glaciers had negative height.

So next Joe raves about seismic waves
   And runs out to buy T.N.T.
But it came to pass that each change in mass
   Was just what we’d blown to debris.
He thought he’d shoot for the theory route
   With area-volume scales;
So Joe would divide feet-long by leagues-wide
   And end up with volume in bales.

Said Joe, “I guess the I.G.S.
   Are a bunch of clever sots,
They’re hosting some sym-pos-i-um
   So I’ll go expound my thoughts.”
He showed fifty-six slides dense as bricks
   With text in Comic Sans
And spoke with such flair that the Session Chair
   Dragged him offstage with both hands.

We went for beers with our glacial peers
   And they told us of what they did
And all this news made Joe enthuse
   Like a sweet-shop-dwelling kid.
So back we went to our field tent
   To add to our data stores
Energized anew, we both set to
   The task of drilling cores.

We drilled and cored and dug and bored
   ‘Til our hands were sore and tired
And I strained my eyes to analyze
   The samples we acquired.
Well, day by day went on this way
   And the data rose like the tide
But nary a bit of that data would fit
   No matter how hard Joe tried.

“I’ll never know how the glaciers flow,”
   Joe cried out in despair
“From the top to the bed, it’s all over my head–
   I tell you, it just ain’t fair.”
“I know some folks can use full Stokes
   But my models ain’t even one-D.
From densification to surface ablation
   These glaciers befuddle me.”

And after this spiel, Joe turned on his heel–
   And threw himself down a moulin!
With a rope from the sledge I raced to the edge
   But by then he was long gone.
Unhappy and damp I returned to the camp
   And pondered poor Joe’s fate;
Down the hole he’d been flushed to be frozen or crushed
   It was awful to contemplate.

But later that night in the fading light
   I awoke to a bellow grand
Like a trumpet brass from a deep crevasse
   Saying “NOW I understand!”
“It’s all so clear from way down here!”
   Exclaimed the voice with glee.
“Every wax and wane of stress and strain
   Is an open book to me!”

“I can see each kernel of snow and firn’ll
   Become a crystal grain
And each drop of melt makes its presence felt
   In the branched subglacial drain.”
The ice folks say that to this day
   A student or a seeker
Can strain an ear, and faintly hear
   From beneath the ice: “Eureka!”

There are strange things done ‘neath the midnight sun
   By those studying ice and snow
Yes, they’re all bizarre, but the oddest by far
   Was the one called Glacier Joe.

Firn Chantey

This is about the work I’ll be presenting at AGU. Written at the request of the University of Alaska Fairbanks crowd, sung to the tune of The Sailor’s Prayer (not to be confused with the somewhat more serious “Sailor’s Prayer” that’s the first Google result for that song title.) I very much want to record all these and post videos, but I haven’t really worked out a good recording setup.

If we wish to learn
About the firn
Upon the ice sheets polar
We’ll want to know
About the snow-
fall and the input solar

Chorus: Oh, snow is white
And clean, and bright
A tricky thing to model
But easy flowed
The Matlab code
‘Longside a friendly bottle

Some grains of snow
Will slowly grow
While others are a-shrinkin’
Which ones win out
Is still in doubt
And needs a bit of thinkin’

(chorus)

Grains change their state
They sublimate
From many different places
When they commence
To recondense
They prefer partic’lar faces

(chorus)

And so we find
Grains are aligned
C-axes all together
And from this state
We can relate
Ice flow to ancient weather

(chorus)
(chorus again, with FEELING)

The Ballad of AGU

The American Geophysical Union Fall Meeting (usually just referred to as AGU) is when something like 15,000 scientists descend on San Francisco’s Financial District for a week. There are talks and posters, of course (so many talks and posters!) but as with any convention the main point is to connect with new colleagues and re-connect with old friends. This is a poem I wrote for the Cryosphere gathering at AGU a couple of years ago. The meter and rhyme scheme are modeled after “The Egyptian Diamond” by Randall Garrett.

I will be at AGU again next week! Monday is Science Open Mic Night at Jillian’s Billiards Club, so I have to decide what to perform, which is going to be tricky.

The Ballad of AGU

Sunday, just a bit past five
And you’re feeling half alive
With your poster on your shoulder as you stumble to your flight
You’ve been staying up too late
Your data won’t cooperate
And you found a whole new error around ten PM last night.

But now you’re at AGU
There’s a million things to do
There are friends from far-off places who you haven’t seen all year
In the morning, though, I’m betting
You will find yourself regretting
That moment you decided “Sure, I’ll have another beer!”

Bright and early, you will fight
The grand excesses of last night
You will struggle bravely out of bed and stagger to Moscone
There’s a talk you must attend
By an early-rising friend
And a cutting-edge announcement you suspect might be baloney

Now you’ve coffee cup in hand,
with which to aid your mental band-
width, for a firehose of data’s aimed directly at your brain
There’s a clever new device
To gauge the temperature of ice
And a host of novel ways to watch a glacier from a plane

There’s a brand-new data set
Barely even processed yet
That details the Greenland ice sheet’s elevation, shape and speed
There’s a fellow at a booth
Who, if his pitch has any truth
Sells an instrumental system that does everything you need

There’s an algorithmic way
To take the data from a day
And extrapolate behavior of the system for a week
There’s a dozen gloomy talks
On how the planet’s on the rocks
And the global warming outlook’s gotten just a bit more bleak

Then, before you’re really read
When your spiel is still unsteady
You’re onstage—your poster’s posted and your work you must explain
Visitors interrogate you
Some to praise, some to deflate you
And your voice is going hoarse from giving out the same refrain

But look! some kind soul brought beer
And the end is getting near
And suddenly it’s over, just as quick as it begun
Battling through the teeming streets
You reach a trove of drinks and treats
And the denizens of Cryosphere are here to have some fun!